docs: def in_bulk(self, id_list):
          """
          Returns a dictionary mapping each of the given IDs to the object with
          that ID.
          """
          if not id_list:
              return {}
          qs = self._clone()
          qs.add_filter(('pk__in', id_list))
          qs._clear_ordering(force_empty=True)
          return dict([(obj._get_pk_val(), obj) for obj in qs])